1. Field of the Invention
The present invention concerns devices for heating food on meal trays, for example for distributing meals in institutions, canteens, hospitals.
The invention is more partially directed to devices of this kind in which the food is heated by induction heating.
2. Description of the Prior Art
Devices of this kind for heating food are already known in themselves, as described in document FR 2 383 637 A, for example, including means for supporting a series of trays one above the other with a suitable distance between them and a series of induction shelves containing induction coils connected to a high-frequency generator, the induction shelves fitting between the successive trays in a tray heating area.
The food to be heated is placed on thin aluminum plates placed on an insulative material tray, the plates being covered by a removable insulative cloche with its inside face coated with a metallic film.
A high-frequency alternating current flows through the induction coils, generating a high-frequency alternating magnetic field in the tray heating area that heats the thin aluminum plate and the metallic bottom face of the cloche by magnetic induction.
A device of the above kind requires aluminum plates. Apart from the fact that this considerably complicates cleaning or requires disposable plates, the food is contained directly in the thin aluminum plate which constitutes a container that is not agreeable for the consumer and may be damaged by the necessary handling of the dishes during use.
Slow heating and uneven heat distribution also occur.
Uneven heat distribution is also encountered with the magnetic steel plate device described in document EP 0 666 047 A, with the bottom electrical element heating device described in document FE 2 375 853 A, with the cloche device provided with an anti-condensation internal metallic heating plate described in document DE 195 07 083 A or with the containers with peripheral and bottom external metallic plates described in document EP 0 203 883 A.
The problem addressed by the present invention is that of designing a new meal tray structure for heating food by magnetic induction in which any type of plate or other food container can be used and which significantly increases the rate of heating and assures an even distribution of heat in the food.
The meal tray of the invention must further have satisfactory qualities in terms of meeting hygiene standards, enabling efficient cleaning and totally preventing the risk of the growth of bacteria and other pollutants.
Furthermore, it must be possible to manufacture the meal tray structure at reasonable cost.